[PATCH] vhost: avoid potential null pointer access

[Li Feng]

Sorry, ignore this patch, there is a rebase error.
I will fix it in V2.


> On 30 Aug 2023, at 4:47 PM, Li Feng <fengli at smartx.com> wrote:
> 
> If the user calls rte_vhost_vring_call() on a ring that has been
> invalidated, we will encounter SEGV.
> 
> We should check the pointer firstly before accessing it.
> 
> Signed-off-by: Li Feng <fengli at smartx.com>
> ---
> lib/vhost/vhost.c |  7 ++++---
> lib/vhost/vhost.h | 12 ++++++++++--
> 2 files changed, 14 insertions(+), 5 deletions(-)
> 
> diff --git a/lib/vhost/vhost.c b/lib/vhost/vhost.c
> index eb6309b681..3af0307cd6 100644
> --- a/lib/vhost/vhost.c
> +++ b/lib/vhost/vhost.c
> @@ -1327,6 +1327,7 @@ rte_vhost_vring_call(int vid, uint16_t vring_idx)
> {
> 	struct virtio_net *dev;
> 	struct vhost_virtqueue *vq;
> +	int ret = 0;
> 
> 	dev = get_device(vid);
> 	if (!dev)
> @@ -1342,13 +1343,13 @@ rte_vhost_vring_call(int vid, uint16_t vring_idx)
> 	rte_rwlock_read_lock(&vq->access_lock);
> 
> 	if (vq_is_packed(dev))
> -		vhost_vring_call_packed(dev, vq);
> +		ret = vhost_vring_call_packed(dev, vq);
> 	else
> -		vhost_vring_call_split(dev, vq);
> +		ret = vhost_vring_call_split(dev, vq);
> 
> 	rte_rwlock_read_unlock(&vq->access_lock);
> 
> -	return 0;
> +	return ret;
> }
> 
> int
> diff --git a/lib/vhost/vhost.h b/lib/vhost/vhost.h
> index 9723429b1c..f38e6d16c9 100644
> --- a/lib/vhost/vhost.h
> +++ b/lib/vhost/vhost.h
> @@ -930,7 +930,7 @@ vhost_vring_inject_irq(struct virtio_net *dev, struct vhost_virtqueue *vq)
> 		dev->notify_ops->guest_notified(dev->vid);
> }
> 
> -static __rte_always_inline void
> +static __rte_always_inline int
> vhost_vring_call_split(struct virtio_net *dev, struct vhost_virtqueue *vq)
> {
> 	/* Flush used->idx update before we read avail->flags. */
> @@ -953,13 +953,17 @@ vhost_vring_call_split(struct virtio_net *dev, struct vhost_virtqueue *vq)
> 				unlikely(!signalled_used_valid))
> 			vhost_vring_inject_irq(dev, vq);
> 	} else {
> +		if (!vq->avail)
> +			return -1;
> +
> 		/* Kick the guest if necessary. */
> 		if (!(vq->avail->flags & VRING_AVAIL_F_NO_INTERRUPT))
> 			vhost_vring_inject_irq(dev, vq);
> 	}
> +	return 0;
> }
> 
> -static __rte_always_inline void
> +static __rte_always_inline int
> vhost_vring_call_packed(struct virtio_net *dev, struct vhost_virtqueue *vq)
> {
> 	uint16_t old, new, off, off_wrap;
> @@ -968,6 +972,9 @@ vhost_vring_call_packed(struct virtio_net *dev, struct vhost_virtqueue *vq)
> 	/* Flush used desc update. */
> 	rte_atomic_thread_fence(__ATOMIC_SEQ_CST);
> 
> +	if (!vq->driver_event)
> +		return -1;
> +
> 	if (!(dev->features & (1ULL << VIRTIO_RING_F_EVENT_IDX))) {
> 		if (vq->driver_event->flags !=
> 				VRING_EVENT_F_DISABLE)
> @@ -1030,6 +1037,7 @@ restore_mbuf(struct rte_mbuf *m)
> 		rte_mbuf_iova_set(m, rte_mempool_virt2iova(m) + mbuf_size);
> 		m = m->next;
> 	}
> +	return 0;
> }
> 
> static __rte_always_inline bool
> -- 
> 2.41.0
>